Dynamic Compression Ratio

[Autoholic]

Thanks for that cam info Jay. Learning more about this engine is very, very enjoyable. As for oval exhaust ports...



This might just be a ported job and not a specially cast head. I would figure this would flow better than a D shaped port.

[Nightmist66]

I can't remember exactly on the experimental higher ratio rockers, but if the ratio is increased on them, will they need to be repositioned differently on the head to allow for the added ratio or will it not change enough to require any other mods? Sorry for the dumb question. It's surprising that the factory head had the d shape exhaust port but it is "upside down" compared to how it is normally used. At least they got the shape right. Factory head on the left.

[jayb]

Those are my heads, Joe, and that is from the porting job - Jay

[jayb]

I can't remember exactly on the experimental higher ratio rockers, but if the ratio is increased on them, will they need to be repositioned differently on the head to allow for the added ratio or will it not change enough to require any other mods? Sorry for the dumb question.

Not a dumb question, since the rocker shaft location is fixed by the mounting points in the heads.  I was going to change the rocker shaft to a smaller diameter, and move it in the mounting points with some offset bushings, to position the pivot point of the rocker closer to the cam.  With the dimensions I was working with, I figured I could increase the ratio to 1.5:1.  We'll see at some point if that will work...

[Nightmist66]

Thanks Jay, that makes sense. Good luck on the project. Iirc, wasn't Mario and Bill C helping out with the R&D?

[Autoholic]

Those are my heads, Joe, and that is from the porting job - Jay

How much material was removed? It doesn't look like too much was removed but you managed to reshape the exhaust port. Would love to know more about the porting work that was done, any issues you ran into.

[Barry_R]

I had some really radically modified heads on my 527 SOHC a few years ago.  They had a ton of weld and some rather small sideways oval shaped exhaust ports along with severely raised intakes.  Engine worked extremely well and is driving in a Galaxie somewhere in PA.  Sold it 'cuz I needed the money (story of my life...).

[Autoholic]

Any pictures of those heads? Can you weld aluminum heads?

[Barry_R]

Engine was written up in Engine Masters Magazine a few years ago now - lot of pics.
I can't weld worth a damn - but I live 20 minutes away from John Marcella.